I'm wondering why the total size (1922860848) isn't the same as Used+Available (1825185124)? From this answer I see that 5% of the disk might be reserved for root, but that would still only take the total used to 1921328166, which is still off. Is it related to some other filesystem overhead?

In case it's relevant, lsof -n | grep deleted shows no deleted files on this disk, and there are no other filesystems mounted inside this one.

Can you elaborate a bit? Why the multiplication by 4?
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Timothy JonesNov 29 '11 at 0:54

df counts in 1k blocks, but the actual filesystem block size is 4k (see tune2fs Block size), so you need to multiply the reserved block size by four to normalize it to compare with the df output.
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Matthew IfeNov 29 '11 at 0:56

So it is, thanks! Do you know why the total size (488378624 * 4 = 1953514496) is larger than the df total size?
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Timothy JonesNov 29 '11 at 0:58

I edited my previous comment to help explain that for the most part..
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Matthew IfeNov 29 '11 at 1:40